JPH1059749A - Production of coated optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dissolve the following problems: Recently mass production of a coated optical fiber and cost reduction thereof a required and production processes, etc., of the coated optical fiber are speeded up to attain production thereof of over 1000m per minute. With the speeding-up of the product processes, amount of tarry organic substances generated at the time of curing a UV ray curing resin applied on the optical fiber increases and the tarry organic substances cannot be entirely removed only by forced exhaust. The residue sticks to the inwall of a quartz tube and UV ray transmission intensity of the quartz tube is lowered. In order to prevent incompleteness or resin setting from occurring, production operation of the coated optical fiber is interrupted to execute cleaning of the inwall of the quartz tube. Thereby, continuous productivity of the coated optical fiber is hindered. SOLUTION: The coated optical fiber is manufactured by applying the UV rays curing resin on the optical fiber made of quartz glass and curing the UV ray curing resin with UV rays. In this case, the optical fiber coated with the UV ray curing resin is passed in the quartz tube 10 the inner surface of which is coated with titanium oxide 10a and the optical fiber coated with the UV ray curing resin is irradiated with UV rays from outside of the quartz tube 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a coated optical fiber in which an ultraviolet curable resin applied to an optical fiber is cured by irradiating it with ultraviolet light.

[0002]

2. Description of the Related Art FIG. 2 schematically shows a general apparatus for manufacturing a coated optical fiber having two coating layers. With this manufacturing apparatus, a coated optical fiber having two coating layers is manufactured as follows. That is, the optical fiber preform 1 is heated and melted in the drawing furnace 2, and the resin is applied to the optical fiber 4 having passed through the outer diameter measuring device 3 by the resin application device 5. Next, the resin coated optical fiber 6 is passed through a resin curing device 7 to cure the resin, thereby obtaining a coated optical fiber 12 having a single coating layer. Further, a resin is applied to the coated optical fiber 12 by a resin coating device 13, and then the resin-coated optical fiber 14 is passed through a resin curing device 15 to cure the resin, and a coated light having two coating layers is formed. The fiber 20 is used. Thereafter, the coated optical fiber 20 is taken up by a take-up capstan (not shown) and wound up on a take-up bobbin (not shown).

[0003] As a resin applied to an optical fiber, a thermosetting resin or an ultraviolet curable resin is commonly used. However, in recent years, an ultraviolet curable resin has been used because it can be cured even when drawn at a higher speed. Resins are often used. When coating an optical fiber or a coated optical fiber (hereinafter simply referred to as an optical fiber) with an ultraviolet curing resin, the ultraviolet curing resin is supplied into the resin coating devices 5 and 13 and the ultraviolet curing devices 7 and 15 are supplied. Is an apparatus having an ultraviolet irradiation mechanism. The ultraviolet irradiation devices 7 and 15 include quartz tubes 10 and 18 through which optical fibers 6 and 14 coated with an ultraviolet curable resin pass, and an ultraviolet light source 9 that irradiates ultraviolet rays from outside the quartz tubes 10 and 18. The apparatus includes an outer wall 11 and an outer wall 17 having an ultraviolet reflective layer on the inner surface. The curing reaction of the ultraviolet curable resin by the resin curing devices 7 and 15 involves generation of a tar-like organic substance, and the generated tar-like organic substance adheres to the inner walls of the quartz tubes 10 and 18 and the quartz tube 10 and 18 weakens the intensity of the ultraviolet light that passes through. If the UV transmission intensity is weakened, the problem of incomplete curing of the resin occurs, so the quartz tube 1
The tar-like organic substances are removed to the outside of the quartz tubes 10 and 18 by forcibly exhausting the atmosphere in the tubes 0 and 18.

[0004]

However, in recent years,
From the demand for mass production of coated optical fiber and cost reduction,
The manufacturing process of coated optical fiber has been accelerated,
000m. Along with this increase in speed, the amount of tar-like organic matter generated when the ultraviolet curable resin applied to the optical fiber is cured also increases, and it becomes difficult to remove all of the tar-like organic matter only by forced evacuation, There is a problem that the residue adheres to the inner wall of the quartz tube and weakens the ultraviolet ray transmission intensity of the quartz tube. In order to prevent incomplete curing of the resin, the manufacturing operation of the coated optical fiber must be interrupted and the inner wall of the quartz tube must be cleaned.
This hinders the continuous productivity of coated optical fibers.

[0005]

Means for Solving the Problems In order to solve the above-mentioned problem, the present inventors have developed a low molecular weight substance which is difficult to adhere to the inner wall of a quartz tube by photochemically decomposing the above-mentioned tar-like organic substance using ultraviolet rays. I decided to convert it. Next, as a result of earnestly examining various substances having photocatalytic action,
It has been found that titanium oxide plays an extremely large role in curing the ultraviolet curable resin used for the coated optical fiber.

That is, the present invention relates to a method for manufacturing a coated optical fiber in which an ultraviolet-curable resin is applied to an optical fiber made of quartz glass and the ultraviolet-curable resin is cured by ultraviolet rays. A method for producing a coated optical fiber, comprising: passing a fiber through a quartz tube having a surface coated with titanium oxide, and irradiating ultraviolet rays to the optical fiber coated with the ultraviolet curable resin from outside the quartz tube. I do.

[0007]

Embodiments of the present invention will be described below in detail with reference to the drawings.

The apparatus for manufacturing the coated optical fiber used in the present invention is basically the same in construction as the apparatus of FIG. 2 described in the section of the prior art, but in the present invention, the quartz tubes 10 and 18 are
As shown in FIG. 1, a titanium oxide layer 10 was formed on the inner surface of the quartz tube.
a and 18a are used. In the present invention, air supply ports 8a, 16a and air discharge ports 8b, 16b are provided at the ends of the quartz tubes 10, 18 as shown in FIG. It is effective to use the forced exhausting by the forced exhausting devices 8c and 16c in order to further secure the object of the present invention. However, in the present embodiment, description will be made by taking as an example the manufacture of a coated optical fiber having two coating layers.

In this embodiment, a coated optical fiber having two coating layers is manufactured as follows. That is, the optical fiber preform 1 is heated and melted in the drawing furnace 2, and the resin is applied to the optical fiber 4 having passed through the outer diameter measuring device 3 by the resin application device 5. Next, the resin coated optical fiber 6 is passed through a resin curing device 7 to cure the resin, thereby obtaining a coated optical fiber 12 having a single coating layer.
Further, a resin is applied to the coated optical fiber 12 by a resin coating device 13, and then the resin-coated optical fiber 14 is passed through a resin curing device 15 to cure the resin, and a coated light having two coating layers is formed. The fiber 20 is used. Thereafter, the coated optical fiber 20 is taken up by a take-up capstan (not shown) and wound up on a take-up bobbin (not shown).

In the production method of the present invention, a part of the tar-like organic matter generated when the ultraviolet-curable resin is cured by ultraviolet rays reaches the inner wall of the quartz tube without being completely exhausted. However, conventionally, the tar-like organic matter that had been deposited on the inner wall of the quartz tube comes into contact with the layer of titanium oxide provided on the inner wall of the quartz tube, and is easily vaporized due to the photocatalytic action of the titanium oxide by the energy of ultraviolet rays. Decomposed into substances. Therefore, the tar-like organic matter does not adhere to and accumulate on the inner wall of the quartz tube, and the ultraviolet ray transmission intensity of the quartz tube is maintained at a level sufficient to completely cure the resin.

In the present invention, even if the production speed of the coated optical fiber is set to 1,000 m / min or more, the ultraviolet ray transmission intensity of the quartz tube is maintained. Although the detailed mechanism of the decomposition reaction of the tar-like organic substance is not clear, an ultraviolet curable resin used for coating the optical fiber, for example, a urethane acrylate resin, an epoxy acrylate resin, a silicone acrylate resin, etc. It has been confirmed by the inventors that only titanium exerts the above-mentioned photolysis catalytic action.

In the manufacturing method of the present invention, the titanium oxide layer is formed by thermal spraying of titanium oxide, flame deposition method such as titanium halide (VAD method, MOCVD method, etc.), and hydrolysis deposition of organic titanium compound such as organic titanate. It is formed by a sintering method or the like. Among these methods, a particularly preferable forming method is a flame deposition method such as a titanium halide (for example, titanium tetrachloride). The titanium oxide layer is preferably empirically made of anatase-type titanium oxide. This is probably because anatase-type titanium oxide has high light semiconductivity.

The thickness of the titanium oxide layer may be any value as long as it does not lower the ultraviolet ray transmission intensity of the quartz tube.
It is preferably in the range of 1 mm. This is 0.1mm
This is because a thicker titanium oxide layer unnecessarily reduces the ultraviolet light transmission intensity of the quartz tube, and a titanium oxide layer having a thickness of less than 0.0005 mm does not provide sufficient catalytic action of titanium oxide. Note that the production speed of the coated optical fiber is 1,0.
In the case of not less than 00 m / min, the thickness of the titanium oxide layer is preferably in the range of 0.001 mm to 0.1 mm. This is because an increase in the production speed of the coated optical fiber relatively increases the amount of tar-like organic matter generated when the ultraviolet curable resin is cured.

In the above-described embodiment of the present invention, a method of manufacturing a coated optical fiber having two coating layers immediately after drawing an optical fiber has been described as an example. When the coated optical fiber coated with the ultraviolet curable resin is further coated, it can be widely applied to, for example, the production of a colored optical fiber, the production of a tape-type optical fiber, the production of an optical fiber unit, and the like.

[0015]

【Example】

Examples and Comparative Examples Hereinafter, Examples and Comparative Examples will be specifically described. In the example, the coated optical fiber 20 was manufactured at a manufacturing speed of 1,200 m / min by the manufacturing apparatus shown in FIG. 2 using the quartz tubes 10 and 18 shown in FIG. A titanium oxide layer was formed on the inner walls of the quartz tubes 10 and 18 of FIG. 1 by a CVD method using TiCl ₄ as a raw material so as to have a thickness of 0.005 mm. In this embodiment, the optical fiber 4 leaving the drawing furnace 2 has a diameter of 125 μm.
m, the outer diameter of the coated optical fiber 12 after the first layer was cured was 190 μm, and the outer diameter of the coated optical fiber after the second layer was cured was 250 μm. Here, the UV-curable resin used for coating is a UV-curable urethane acrylate resin for both the first and second layers. Further, the inside of the quartz tube of the ultraviolet irradiation device was forcibly evacuated by flowing nitrogen.

As a measure of continuous manufacturability, the UV transmission intensity ratio of the quartz tube after continuous coating of the UV curable resin for 120 hours ((UV transmission intensity after operation / UV transmission at start of operation) Strength) x 100). Further, the degree of contamination of the quartz tube by the tar-like organic matter generated during curing of the ultraviolet curable resin was visually observed at the same time as the above.

In the comparative example, a coated light having two coating layers was used under the same conditions as in the embodiment except that the quartz tube 10 was not provided with a titanium oxide layer on the inner surface as shown in FIG. A fiber 20 was manufactured. It should be noted that the evaluation of the continuous production and the observation of the degree of contamination of the quartz tube were performed on the comparative example as in the example.

Table 1 summarizes the results obtained in the Examples and Comparative Examples.

[0019]

[Table 1]

From Table 1, it was found that the production method of the present example according to the present invention had a significantly higher continuous productivity than the production method of the comparative example.

[0021]

According to the present invention, there is provided a method for producing an optical fiber in which an ultraviolet curable resin is applied to an optical fiber made of quartz glass and the ultraviolet curable resin is cured by ultraviolet rays. By passing ultraviolet light from the outside of the quartz tube to the optical fiber coated with the ultraviolet curable resin through the inside of a quartz tube coated with titanium oxide on the inner surface, thereby generating at the time of light curing of the ultraviolet curable resin. The decrease in the ultraviolet transmittance of the quartz tube caused by the adhering and depositing of tar-like organic substances on the inner wall of the quartz tube is remarkably reduced. Specifically, even when the coated optical fiber is manufactured at a high speed of 1,000 m / min or more, continuous manufacturing for an extremely long time becomes possible.

[Brief description of the drawings]

FIG. 1 is a sectional view of a quartz tube according to the present invention.

FIG. 2 is a schematic view of an embodiment of a coated optical fiber manufacturing apparatus according to the present invention.

FIG. 3 is a sectional view of a quartz tube used in a comparative example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 optical fiber preform 2 wire drawing furnace 3 outer diameter measuring device 4 optical fiber 5, 13 resin coating device 7, 15 resin curing device 8a, 16a air supply port 8b, 16b air discharge port 8c, 16c forced exhaust device 9, 17 Ultraviolet light source 10, 18 Quartz tube 10a, 18a Titanium oxide layer 20, 12 Coated optical fiber

Claims (1)

[Claims] 1. A method of manufacturing a coated optical fiber in which an ultraviolet curable resin is applied to an optical fiber made of quartz glass and the ultraviolet curable resin is cured by ultraviolet rays. A method of manufacturing a coated optical fiber, comprising: passing an ultraviolet ray from outside of the quartz tube onto the optical fiber coated with the ultraviolet curable resin through a quartz tube coated with titanium oxide.